Hydroconversion process utilizing a water-washed asphalt feedstock

ABSTRACT

A process for removing water-soluble salts from asphalt by first blending the asphalt with a hydrocarbon solvent, preferably predominantly aromatic, and then washing the diluted asphalt with water. Hydroconversion, e.g. hydrocracking or desulfurization, of such desalted asphalts over a catalyst, preferably disposed as a fixed bed, results in increased maintenance of catalyst activity which eventually lines out at a higher level than catalysts employed in hydroconverting unwashed asphalts.

United States Patent Stanley C. Haney llomewood;

Edward W. Remus, Buffalo Grove, both of III.

Jan. 15, 1969 Nov, 2, 197 1 Atlantic Rlehfield Company Inventors Appl. No. Filed Patented Assignee HYDROCONVERSION PROCESS UTILIZING A WATER-WASHED ASPHALT FEEDSTOCK 12 Claims, No Drawings U.S. Cl 208/88, 208/251 lnt.Cl Cl0g 31/08 Field of Search 208/45, 88, 251, 290, 337

Primary Examiner- Delbert E. Gantz Assistant Examiner-G. J Crasanakis Attorney-McLean, Morton and Boustead ABSTRACT: A process for removing water-soluble salts from asphalt by first blending the asphalt with a hydrocarbon solvent, preferably predominantly aromatic, and then washing the diluted asphalt with water. Hydroconversion, e.g. hydrocracking or desulfurization, of such desalted asphalts over a catalyst, preferably disposed as a fixed bed, results in increased maintenance of catalyst activity which eventuallylines out at a higher level than catalysts employed in hydroconverting unwashed asphaltr.

HYDROCONVERSION PROCESS UTILIZING A WATER- WASHED ASPHALT FEEDSTOCK This invention relates to a method of removing water-soluble salts from asphalt. More particularly, the invention relates to a method of removing water-soluble salts of metals such as sodium, calcium, iron and vanadium from asphalt, in which the asphalt is blended with a solvent, washed with water, the water separated, and the asphalt employed as a feedstock to a hydroconversion operation. Preferably the solvent is also separated from the asphalt prior to the latter being used as a feedback for hydroconversion. v

Metal salts have long been known to impair processes for refining crude petroleum oils. Corrosion products such as iron oxides tend to accumulate in asphalts during the refining process. If the asphalt is treated with hydrogen in the presence of a solid catalyst the iron oxide forms deposits in the catalyst bed which cause excessive pressure drops in the system. Metal salts of sodium, calcium, magnesium, vanadium and nickel react with the hydrogen and catalyst and are absorbed on the catalyst surface, thus decreasing catalyst activity. Washing the catalyst with deionized or distilled water removes some of the deleterious metals but the salts of nickel and vanadium are not as receptive to water wash as are the alkaline metals. Furthermore, a significant portion of the active catalyst metals such as cobalt and molybdenum are also removed by such a washing process, thus rendering the catalyst less active. Also, the catalyst crush strength may be lowered by washing and the attrition tendency of the catalyst results in a reduction in catalyst particle size, which in turn contributes to the pressure drop problem.

It is known that alkaline metal salts may be removed from crude petroleum oil by a process of desalting which includes mixing the crude with water, settling and decantingAn additive is frequently employed to minimize the formation of emulsions, allowing the water to settle more quickly. While these methods are suitable for removing contaminating metal salts from crude oil, such methods have not been adequate to remove metal salts from asphalt. It has now been discovered, however, that asphalt can be desalted by first blending the asphalt with a normally liquid hydrocarbon solvent, preferably predominantly aromatic in nature, to produce a mixture which is essentially liquid at ambient conditions of temperature and pressure. Furthermore, when asphalt which has been desalted in this manner is hydroconverted, e.g. desulfurized or hydrocracked, over a catalyst, the activity of the catalyst maintains and eventually lines out a higher activity level than catalyst employed in hydroconverting unwashed asphalt.

The asphalt stock to be desalted by the method of this invention is generally a heavy residual petroleum crude material that contains asphaltenes and maltenes, as for example, penetration range vacuum asphalts having a penetration from about 75 to 250 at 77F. The asphalts employed in this invention are characteristically solids at ambient temperatures although some of these asphalts do tend to flow at such temperatures. The asphalt can be diluted with the hydrocarbon solvent in a volume ration of solvent to asphalt of about 1:1 to 5:1, preferably about l.5:l to 3:]. The asphalt-solvent mixture may be heated to facilitate blending. The solvent employed is normally liquid and boils primarily in the gasoline boiling range and thus primarily of about 6 to 12 carbon atoms. The

' solvent is preferably predominantly, or even at least about 80 weight percent or entirely aromatic, such as xylene, benzene or toluene, with xylene being especially preferred. Ethylbenzenes and cumene can also be used. In addition, aliphatic hydrocarbons having chains of 6 to l2 carbon atoms can be employed.

Washing of the asphaltsolvent mixture with water can be carried out using water in an amount of about 5 to 50 volume percent per pass, based on the total mixture, preferably about 25 to 30 volume percent. A total water wash of about 5 to 150 volume percent, preferably 50 to 100 percent, is normally employed. From I to 5 passes with water, preferably 2 to 3, can be employed but in any event sufficient water is used to remove enough metal contaminants so that the activity of the hydroconversion catalyst is significantly improved. Washing temperatures are often about l50to 250F. The time required.

for the mixing and the subsequent settling and water draw can be varied, depending on the characteristics of the asphalt and the degree of metal removal desired. Also, a continuous unit may be employed similar to the type unit employed in the processing of crude oil. The asphalt-solvent mixture can then be dried, for example by means of a blotter filter press, and the mixture heated by means such as a distillation column to remove the solvent overhead as well as any remaining water. Other satisfactory ways of removing the water, and any portion or all of the solvent, from the asphalt can be employed. The solvent may however remain in the asphalt feed to be hydroconverted.

Hydroconversion of the washed asphalt is carried out in contact with a solid, hydroconversion catalyst. The catalyst is preferably used as a fixed bed, and the pretreatment of the asphalt according to this invention reduces pressure drop in the bed. The various catalysts having hydrogenation activity can be used, but cobalt-molybdenum or nickel-molybdenum carried on an alumina base is preferred. However, the catalyst may also be the metals, oxides or the sulfides, supported on a carrier, or unsupported, of metals of Groups IV, V, VI, and VIII of the periodic system. Examples of suitable catalytic ing'redients are tin, vanadium, members of Group VIB in the Periodic Table, i.e., chromium, molybdenum and tungsten and metals of the iron group, i.e iron, cobalt and nickel. These metals are present in catalytically effective amounts, for instance, about 2 to 30 weight percent, and can be present in the elemental form or in the form of oxides or sulfides. Mixtures of these materials or compounds of two or more of the oxides or sulfides can be employed, for example, mixtures or compounds of the iron group metal oxides or sulfides with the oxides or sulfides of Group VlB constitute very satisfactory catalysts. Examples of such mixtures or compounds are nickel molybdate, tungstate or chromate (or thiomolybdate, thiotungstate or thiochromate) or mixtures of nickel of cobalt oxides with molybdenum, tungsten or chromium oxides. As the art is aware and as the specific examples below illustrate, these catalytic ingredients are generally employed while disposed upon a suitable carrier of the solid oxide refractory type, e.g., a predominantly calcined or activated alumina or alumina combined with silica if cracking activity is desired. Commonly employed catalysts have about I to l0 percent of an iron group metal and 5 to 25 percent ofa Group VlB metal (calculated as the oxide). The fixed bed of catalyst is usually formed by macrosize catalyst particles, e.g. having a diameter of about one thirty-second to one-half inch, preferably about one-sixteenth to one-fourth inch, and if not spherical, a length of one eighth to 1 inch or more, often about one-fourth to threefourth inch.

The hydroconversion step, e.g. hydrocracking or desulfurization, can be carried out under conditions including a temperature of about 700 to 950 F preferably 750 to 875 F., and a hydrogen partial pressureof about 500 to 3,000 p.s.i.g., preferably about l,000 to 2,800 p.s.i.g. The amount of free hydrogen employed is generally about 500 to 20,000 standard cubic feet per barrel of hydrocarbon feed, preferably about 1,500 to 8,000 standard cubic feet per barrel. The weight hourly space velocity (WHSV), weight units of hydrocarbon feed introduced into the reaction zone per hour per weight unit of catalyst, will usually be within the range of about 0.1 to [0, preferably about 0.25 to 2. The products from the hydroconversion are generally of lower boiling range or lesser sulfur or nitrogen content and frequently the product is both purer than the feedstock and of lower boiling range.

The following examples are illustrative of the method of this invention:

Fifty gallons of asphalt was diluted with I00 gallons mixed xylene, resulting in a mixture having a viscosity of 30 to 40 SSU at F. Forty gallons of distilled water was added, after which the mixture was heated to 220 F. and mixed for one hour by a mechanical stirrer. The mixture was allowed to settie for 8 hours and the water then drawn ofi and discarded. At this time a sample of asphalt and xylene mixture was taken. The washing cycle was repeated with the addition of water, heating mixing, settling and discarding of water as before. The mixture was then dried by adding 1 pound of a commercial drying compound such as Supercel and passing the mixture through a blotter filter press. The mixed xylenes were then removed by heating the dried mixture in a distillation column.

Table 1 lists the physical properties of the unwashed asphalt together with the properties of the once and twice washed specimens. it is apparent from an examination of Table 1 that water washing effectively eliminates the major portion of the iron, sodium and calcium and part of the vanadium.

TABLE I Asphalt samples Wash Wash Unwashed N0. 1 N0. 2

Gravity, API 12. 1 11. 6 11. 4 Furol viscosity at 210 F., sec 235 279 365 Carbon residue (con.), wt. percent 14. 39 16. 83 16. 48 Hydrogen content, wt. percent 11. 06 11. 03 11. Sulfur content, wt. percent 1. 69 1. 67 1. 71 Oxygen content, wt. percent 0. 75 0.70 0. 66 Nitrogen content, wt. percent 0. 41 0.41

Metals content, p.p.m.:

Nickel 17 18 26 15 15 52 5 4 3 1 1 75 20 18 60 16 8 Two hydrocracking runs were then carried out with unwashed and twice-washed asphalt serving as feed. The catalysts employed in the two runs were identical charges of a commercially available cobalt-molybdenum on a silica promoted, alumina base. The runs were carried out for a period of over 500 hours at temperatures in the range of 800 to 830 F. and a hydrogen partial pressure of 1,500 p.s.i.g., a weight hourly space velocity of 0.5 to 1.35 and a hydrogen rate of 4,000 standard cubic feet per barrel of feed. Catalyst desulfurization activities were calculated at frequent intervals by correcting all process variables to one common base. The time at which flush catalyst activity had been destroyed was determined to be I07 hours and the catalyst activity at this time was arbitrarily set at 1.0. Table ll lists the relative hydrodcsulfurization activities at various points during the runs for the unwashed and twice-washed asphalt.

TABLE II Relative hydrodesuilurization activity Twice Unwashed washed asphalt asphalt it is claimed: 1. A process for the hydroconversion of petroleum asphalt which comprises:

a. Blending the asphalt with a hydrocarbon solvent containing about six to 12 carbon atoms in an amount sufficient to give a normally liquid mixture,

b. Washing the asphalt-solvent mixture with water to remove salts of metals selected from the group consisting of iron and vanadium from the asphalt,

c. Removing water from the asphalt-solvent mixture, and

d. Passing the washed asphalt and hydrogen under hydroconversion conditions, at a temperature of about 700 to 950 2 F., in contact with a hydroconversion catalyst.

2. The process of claim 1 wherein the solvent is selected from a group consisting of xylene, toluene, and benzene.

3. The process of claim 1 wherein the asphalt fraction is blended with solvent in a volume ratio of solvent to asphalt fraction of about lzl to 5:1.

4. The process of claim 1 wherein the quantity of water employed is about 50 to volume percent, based on the total mixture.

5. The process of claim 4 wherein the water wash employs from one to five passes with water.

6. The process of claim 1 wherein the catalyst support consists essentially of silica-promoted alumina.

7. The process of claim 6 wherein the catalyst contains cobalt and molybdenum.

8. The process of claim 7 wherein the hydroconversion conditions include a pressure of about 500 to 3,000 p.s.i.g., a space velocity of about 0.l to 10 WHSV and a hydrogen feed rate of about 500 to 20,000 standard cubic feet per barrel of feed.

9. A process for the conversion of asphalt to lower boiling, normally liquid material which comprises:

a. Blending the asphalt with an aromatic hydrocarbon of about six to 12 carbon atoms in a volume ratio of aromatic hydrocarbon to asphalt of about l:l to 5:1,

b. Washing the asphalt-aromatic hydrocarbon mixture to remove salts of metals selected from the group consisting of iron and vanadium from the asphalt at a temperature of about 150 to 250 F. by the method comprising from I to 5 passes with water, each pass comprising the addition of water in an amount of about 5 to 50 volume percent, based on the total mixture, allowing the mixture to settle and decanting the asphalt layer,

c. Drying the asphalt-aromatic hydrocarbon mixture,

d. Heating the asphalt-aromatic hydrocarbon mixture sufficiently to remove the aromatic hydrocarbon and any remaining water, and Passing the washed asphalt fraction and hydrogen under hydrocracking conditions at a temperature of about 700 to 950 F., a pressure of about 500 to 3,000 p.s.i.g., a space velocity of about 0.1 to 10 WHSV and a hydrogen feed rate of about 500 to 20,000 standard cubic feet per barrel of feed, in contact with a fixed bed of hydrocracking catalyst.

10. The process of claim 9 wherein the catalyst is comprised of cobalt and molybdenum on a silica-promoted alumina base.

11. The process of claim 10 wherein the washed asphalt fraction and hydrogen are passed under hydrocracking conditions at a temperature of about 750 to 875 F., a pressure of about 1,000 to 2,800 p.s.i.g., a space velocity of about 0.25 to 2 WHSV and a hydrogen feed rate of about L500 to 8,000 standard cubic feet per barrel of feed.

12. The process of claim 11 wherein the aromatic hydrocarbon is xylene.

i I it i 

2. The process of claim 1 wherein the solvent is selected from a group consisting of xylene, toluene, and benzene.
 3. The process of claim 1 wherein the asphalt fraction is blended with solvent in a volume ratio of solvent to asphalt fraction of about 1:1 to 5:1.
 4. The process of claim 1 wherein the quantity of water employed is about 50 to 150 volume percent, based on the total mixture.
 5. The process of claim 4 wherein the water wash employs from one to five passes with water.
 6. The process of claim 1 wherein the catalyst support consists essentially of silica-promoted alumina.
 7. The process of claim 6 wherein the catalyst contains cobalt and molybdenum.
 8. The process of claim 7 wherein the hydroconversion conditions include a pressure of about 500 to 3,000 p.s.i.g., a space velocity of about 0.1 to 10 WHSV and a hydrogen feed rate of about 500 to 20,000 standard cubic feet per barrel of feed.
 9. A process for the conversion of asphalt to lower boiling, normally liquid material which comprises: a. Blending the asphalt with an aromatic hydrocarbon of about six to 12 carbon atoms in a volume ratio of aromatic hydrocarbon to asphalt of about 1:1 to 5:1, b. Washing the asphalt-aromatic hydrocarbon mixture to remove salts of metals selected from the group consisting of iron and vanadium from the asphalt at a temperature of about 150* to 250* F. by the method comprising from 1 to 5 passes with water, each pass comprising the addition of water in an amount of about 5 to 50 volume percent, based on the total mixture, allowing the mixture to settle and decanting the asphalt layer, c. Drying the asphalt-aromatic hydrocarbon mixture, d. Heating the asphalt-aromatic hydrocarbon mixture sufficiently to remove the aromatic hydrocarbon and any remaining water, and e. Passing the washed asphalt fraction and hydrogen under hydrocracking conditions at a temperature of about 700* to 950* F., a pressure of about 500 to 3,000 p.s.i.g., a space velocity of about 0.1 to 10 WHSV and a hydrogen feed rate of about 500 to 20,000 standard cubic feet per barrel of feed, in contact with a fixed bed of hydrocracking catalyst.
 10. The process of claim 9 wherein the catalyst is comprised of cobalt and molybdenum on a silica-promoted alumina base.
 11. The process of claim 10 wherein the washed asphalt fraction and hydrogen are passed under hydrocracking conditions at a temperature of about 750* to 875* F., a pressure of about 1,000 to 2,800 p.s.i.g., a space velocity of about 0.25 to 2 WHSV and a hydrogen feed rate of about 1,500 to 8,000 standard cubic feet per barrel of feed.
 12. The process of claim 11 wherein the aromatic hydrocarbon is xylEne. 